Tsoy T D, Kruglova N A, Filatov A V
Institute of Immunology National Research Center, Federal Medical-Biological Agency, Moscow, 115522, Russia.
Lomonosov Moscow State University, Faculty of Biology, Moscow, 119234, Russia.
Biochemistry (Mosc). 2018 Nov;83(11):1380-1387. doi: 10.1134/S0006297918110081.
Lymphocyte phosphatase-associated phosphoprotein (LPAP) is a molecular partner of CD45 phosphatase that plays a key role in the regulation of antigen-specific activation of lymphocytes. The functions of LPAP still remain unknown. We believe that studying LPAP phosphorylation pathways could shed light on its functions. In this work, we studied the phosphorylation of LPAP ectopically expressed in non-lymphoid cells in order to determine the effect of LPAP interaction partners on its phosphorylation. We found that phosphorylation at Ser153 and Ser163 in non-hematopoietic HEK293 cells was conserved, while phosphorylation at Ser99 and Ser172 was almost absent. The pattern of LPAP phosphorylation in K562 erythroid and U937 myeloid cells expressing endogenous CD45 protein was similar to that observed in T and B lymphocytes. We demonstrated for the first time that LPAP is a substrate for protein kinase CK2 that phosphorylates it at Ser153, presumably ensuring LPAP resistance to degradation.
淋巴细胞磷酸酶相关磷蛋白（LPAP）是CD45磷酸酶的分子伴侣，在淋巴细胞抗原特异性激活的调节中起关键作用。LPAP的功能仍然未知。我们认为，研究LPAP磷酸化途径可能有助于揭示其功能。在这项工作中，我们研究了在非淋巴细胞中异位表达的LPAP的磷酸化，以确定LPAP相互作用伙伴对其磷酸化的影响。我们发现，非造血性HEK293细胞中Ser153和Ser163的磷酸化是保守的，而Ser99和Ser172的磷酸化几乎不存在。表达内源性CD45蛋白的K562红细胞和U937髓细胞中LPAP的磷酸化模式与在T和B淋巴细胞中观察到的相似。我们首次证明LPAP是蛋白激酶CK2的底物，CK2在Ser153处使其磷酸化，大概是确保LPAP抗降解。
